Back reflector for radiant energy glass-to-metal sealing means



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. BACK REFLECTOR FOR RADIANT ENERGY GLASSPTO-)IBTAL .v SEALING MEANS "-v A F1ed June 8. 41967 .J Y 1* Y' ATTCRNEY Us. c t. ss-tss 3,460,930 BACK REFLECT OR FOR RADIANT ENERGY GLASS-TO-METAL SEALING MEANS Edward I.. Pityo, Cedar Grove, NJ.. assigner to Federal Tool Engineering Co., Cedar Grove, NJ., a corporation of New Jersey Eled June 8, |967, Ser. t 0. 644,669

' Int. CL C03c 27/02 5 Claims Background of the invention The invention pertains to that form of device kn as a back reflector, used in conjunction with a source of radiant energy, such as an infrared lamp, for delivering the energy to an object to be heated such as the glass o envelope of a magnetic reed switch or the like. In such work, the problem is to collect and concentrate the energy on the object as when sealing glass to a metalpart, and evenly distributing the radiation as completely as possible around the entire circumference of the object.

While the back reflector technique is well known in the art, broadly speaking, serious deficiencies have been present with known types of back reflectors and known techniques. The most serious problem encountered in the Y prior art arises from the utilization of a one-piece'cylindrically curved back reflector in conjunction with a frontal radiant energy source. The object to be heated, such as a reed switch envelope, is typically smaller than the focal z one of the radiation produced and as a result substantial.

portions of the energy zone lie outside of the glass element and are therefore unusable. To offset this, it is necessary to bring the back reflector relatively close to the object being heated, and this gives rise to another major problern or defect. namely, the formation of objectionable oxide deposits from the glass on the highly polished (gold) face of the reflector.

Furthermore, a cylinder presents a flat elemental surface to the energy rays producing divergence and diluation of energy density.

Other prior art techniques involving constant rotation of the object being heated are not entirely practical andv present complex problems of fixturing. Additionally, the possibilities of heating the object from two or more sides are-very limited and therefore the back reflector technique is best suited to the typical situations encountered in the industry.

Summary of the invention`-V A In accordance with the present invention, the above Therefore, while the arrangement of FIGURE 1B in deficiencies of the p rior art pratcice are substantially overcome and eliminated-The invention makes VAuse-of a vrnent allows placement of the glass clement to be heated at a point sufficiently remote from the reflectorfaces to minimize* the tendency for oxide deposits to form on the 3,460,930 Patented Aug. 12, 1969 reflector faces. The invention takes-advantage-inherently of the gap or space between laterally separated reflector..

parts to. totally eliminate objectionable deposits in central area while at the same time allowing the radiant energy to be efficiently concentrated on the worktunit with minimum loss and evenly around the circumference of the work unit. The supporting of the refleor tions FIGURE 4 is an exploded perspective view of the inven" tion.

Description of the preferred embodiment Referring to the drawings whereinlike numerals designatc like parts. attention is directed first to FIGURE lA which graphically illustrates conventional prior art techniques. In FIGURE lA, a radiant energy source, such* WIT-as an infrared source l0. is indicated-Typically; this may-- be a 1000 wat; tungsten filament with avsuitable apprpximately parabolic gold reflector, not shown. A back reflector itis provided in the form of a' cylindrically curved 'oody whose interior surface is gold-plated. The one-piece back reflector 1l. may have mounting extensions I2. The work unit 1 3, sucn as a cylindrical glass tube or envelope fora reed 'sw-itch, is located inwardly of the center of.' curvature 14 of the back reflector 1l. Typical rays l5 emanating from the energy source l0 are shown reflecting from the cylindrical surface of the hack reector at points 16 and enti ely missing the glass object 13. to be heated. The radia.t or heating energy Aone 17 produced by the coaction of the source 10 and back reflector 1l is shown approximately and graphically in broken lines as an ellipse and it is evident in FIGURE lA that the glass element or obiect I3 lies substantially outside of ti.: one 17 except for a relatively small segment of the o zone and consequently the maior part of the reflected heat energy is lost or ineffective to heat the element 13 in FIGURE 1A.

This inefficient prior art aLangement lc'ads logically to the arrangement ofiFIGURE 1B, also a part of the prior art teaching. In this figure, the cylindrically curved' back reflector is shown at l1' and the glass element or envelope is indicated at 13'. As is apparent in FIGURE 1B, the glass element has been moved considerably toward the reflective surface of cylindrical back reflector 1l', to a point more than one-half of the radius of the back reflector closer to the reflective surface. The purpose of this adjustment is to locate the glass element totally within the .confines of the radiant energy zone 17'. However, it. will be noted that this compensation or adjustment gives rise to another serious problem caused by the fact that the melting glass is movedconsiderably closer to the back reflector, whereby metal oxide from the glass has a much greater tendency to condense as a dull gray coating 18 on the reflecting surface, thus destroying its usefulness.

creases the ef iii5tly 9ft he system from the standpoint f-titilii-g more of the available heat energy from the zone 17', simultaneously a new and equally serious problem arises due to placing the glass element too close to the reflective surface and thus encouraging the'formation of the metal oxide deposit 18 thereon. Also, it may be observed in FIGURE 1E that large end portions 19 of the hrw.

`energy zone 17' are still well outside of the space 0ccupied by the element 13 and tlLis energy is thus lost or ineffective to heat the element 13'.

' FIGURES 2-4 inclusive show the invention structure which to a great extent overcomes the difficulties which have been discussed in connection with FIGURES 1A and IB.

Referring to FIGURE 4, a mounting bracket or holder s, 2li is shown including a vertical body portion 2l which may beattached to-a suitable structural element of a reed switch fabricating apparatus or Vthe like. The'holder 20 further comprises back reflector support arms 22 and 23 which are spaced apart lateraliy, there being a connect ing web 24 between these arms, as shown. Spherically curved .back reflector sections 25 and 26 are provided and these sections are spherically curved in both the vertical and horizontal planes. Each reflector section has an end lateral mounting extension or tab 27 having an adjusting slot 28..The extremities of support arms 22 and 23 have machined grooves 29 which receive the tabs 27 and screws 30 serve to adjustably rigidly secure the back reflector sections to the support arms 22 and 23 in desired laterally. adjusted positions perfnittet'Lby the elongated slots 28.'

There will always be a gap or space 3l between recctor sections 25 and 26 and thus it is impossible for the mentioned oxide deposits to accumulate in this region. To further inhibit the formation nf .i on 'my part/ol'fe reflective surface, a forrdl .l P ("ln C e l i' connected with' t na bc rc derer lly atjustnble upon its primary support' so that the back reflector sections can be adjusted in two planes. The re- -flective faces of sections 2S and 26 are gold-plated with 4a highly polished finish for maximum efficiency. y FIGURES 2 and 3 show in a somewhat diagrammatic form the advantages of the invention structure in comparison to the prior art. In FIGURE 2, the infrared source or lamp is indi:^'ed at 33 and the cylindrical glass envelope at 34. The radiant energy zone 35, as shown in FIG- I URE 2, is considerably forcshortened due to the sepa-V rated arrangement of the back reflector sections and the glass envelope may be centered within the zone and spaced suflleiently far from the spherical reflective surfaces so that there will be no serious tendency to cause an oxide formation thereon. The gap or space 31 immediately behind the glass envelope eliminates the oxide coating problem in the most critical area and, as stated, the air stream from the tube 34 continually flowing forwardly through this gap tends to direct any particles of oxide or impurities away from the reflective surfaces.

It may be observed in FIGURE 2 that the axial center of the glass envelope may be positioned considerably less than one-half the radius of a reflector section inwardly of the centers 36, these centers 36 being the true centers of curvature in the horizontal plane of spherically curved back reflector sections 25 and 26. Each such reflector section also has a center of curvature 37 in the verticaltplane as shown in FIGURE 3. Continuing to refer to FIGURE 2,-th centers 36 are spaced equidistantly laterally of a center line 38 through the center of the gap 3l'. A radius for a single sphetieally curved baci: reflector would lie on the center line 38. However, a significant feature of the present invention resides in spac' ing the centers 36 equidistantly on opposite sides of the center line 38 so that energy rays 39 from the source 33 will be reflected from points 40 on spaced reflector sections 25 and 26 back onto the glass envelope 34, rather than wide of the same as in FIGURE 1A. As a result of the invention arrangement, the heat energy zone 35 is much less elongated and much less of the available heat energy is lost or unused on opposite sides of the envelope 44 as graphically illustrated in FIGURE 2. Consequently, the geometry of the parts in FIGURE 2 is such that the r 4 heating of the glass element 34 efficiently and uniformly around its circumference is greatly increased and the tendency for oxide deposits to condense` on the spherical reflected surface is greatly decreased', thus satisfying lthe two main objectives of the invention.

FIGURE 3 depicts graphically the advantage gained by having each reflector section curved in the vertical plane,

'as contrasted to thestraight cylindrical back reflector Il' of the prior art. ln FIGURE 3, an incoming energy ray 4l is reflected at 42 from back' reflector ll' and misses entirely the glass envelope 34 as indicated at 43.'How ever, the same ray 4l reflected at 44 from the spherical reflector section 25 passes directly onto the upper portion of the glass envelope as indicated at 45, for example, as during the forming of the upper glass seal of a reed switch or like device.

In this connection, it should be understood that the reflector sections 25 and 26 may be employed in upper and lower pairs in a reed switch fabricating apparatus so as to be capable of producing upper and lower glass seals on each switch in cooperation with a vertically shift` able radiant energy source.

The spherical shape in the vertical Plane of reflector sections 2S and 26 may notv represent the ideal curvature, but this construction renders fabrication of the back reflector much simpler since the horizontal curvature is circular. The spherical configuration satisfies the requirements or criteria for the invention very nicely. The light pattern is strongly divergent as it -leaves the glass seal area. Thiswliglit-'or venergy must be collected and rei turned te. the seal area in a convergent pattern or ctherwise theenergy density is diluted and the pattern is wider on the back side than on the front. t r` s Essentially, the invention structure has accomplished the followingffhe light pazh or energy path is directional and the pattern is rapidly converging and divcrging as it enters and leaves the focal zone 17-35. The energy rays` falling outside of the glass object in simple terms totally misses the target-As previously'mentioned, .here are two end zones of energy that are available for further work but are ordinarily wasted; the outer ends 19 of the focal. zone that have missed the glass, the center portion of the zone having been absorbed by the glass on the first pass ofthe rays and therefore unavailable for further work. In order to manipulate these two potential energy sources and direct them to the rear portion of the glass seal, concave optics is employed by the invention to collect the divergent rays and cause them to converge on the seal area. Since there are two separated zones of energy as Y described, the concave opties is divided in the invention to handle both zones properly. It is believed that in view of the drawings and the above description, the advantages of the invention over the prior art will new be readily apparent to those skilled in the art without the necessity for any further description.

Iclaim:

l. A back reflector structure for heat sealing glass envelopes of'rced switches and the like in cooperation intermediate connecting portion, a pair of separately formed approximately v.sp'hericallycurved back reflector elements having forward concave reflecting surfaces and arranged rearwardly of the glass envelope to be sealed, means for adjustably securing each baci'. reflector element to one of said arms so that each back reflector element is rendered independently adjustable la rally relative to the other element to establish a centigap of desired width between the back reflector elem nts, anda fluid nozzle connected in said intermediate portion of the supporting bracket for directing a fluid jet forwardly through said gap to inhibit and retard the formation of oxide deposits on said concave reflecting surfaces.

2. A back reflector structure as defined by claim l,

f.- 3f A back reflector stru:ture as defined by claim 1,

wherein said means for adjustably securing comprises l guide groove in the forward end of each bracketarm, a lateral extension on the outer forward end of cach back reflector element and being slidably engageable within 6 with said intermediate portion substantially midway between said arms, and a pair of back refieccr elements having forward approximately spherically curved concave retiecting surfaces and lateral mounting extensions engageable with the forward ends of said arms, and

means to clamp said extensions adjustably to the forward ends of said arms and enabling each back reflector element to be independently adjusted laterally relative to the ow axis of the nozzle devioe.

onejof said grooves and having a slot formed there- 4 through, and a threaded fastener element engaging' through each slot and having screw-threaded engagement with one of said arms.

4. A back reflector structure for use in conjunction with a frontal source of radiant energy for heat sealing a glass envelope of a reed switch or the like located be tween said frontal source and structure, said structure comprising a unitary supporting racket adapted to be secured to a reed switch fabricating unit and including a pair of laterally spaced arms and an intermediate portion connecting said arms adjacent the rear ends of the arms, a

central forwardly opening fluid nozzle device connected 5. A back reflector structure as defined by claimv 4,

I and a lateral guide surface on each arm slidably engaging one of said extensions.

References Clfetl UNITED STATES PATENTS 8/1893 Severy 126-270 2/ 1967 Drake 65-155 s LEON Bastione, Primary Examiner E. R. FREEDMAN, Assistant Examiner I U.S. Cl. XR. 

